Enzymes are useful as catalysts in various chemical reactions, and are preferably used in a purified form, separated from the organism that produced them. In such a purified form the enzyme is relatively unstable and easily denatured. It is also recovered with difficulty from an aqueous reaction medium. To overcome these difficulties, it is desirable to immobilize the enzyme on some insoluble carrier, where it may readily contact the reactants in said reaction medium, but where it benefits both from an increased stability and from easy recovery by simple processes such as filtration.
Ideally, the enzyme support material should possess the following characteristics:
(a) the enzyme immobilization upon the support should be accomplished with ease;
(b) the support should demonstrate chemical and physical stability, for example, to the effects of pH, salt, solvent, and mechanical compression;
(c) the support should be convenient to handle;
(d) the support should accommodate an acceptable loading of enzyme;
(e) the support should tolerate reasonable pressure drop associated with particle size, particle shape and flow rate;
(f) the support should stabilize the enzyme with respect to temperature, pH, salt, solvent and contaminants that might affect denaturation; and
(g) the materials should be stable to storage.
Enzymes can generally be immobilized on a solid support by three different methods: adsorption, covalent attachment or entrapment. Each method possesses its own advantages and disadvantages, but regardless of the method of attachment all immobilized enzyme systems are susceptible to incomplete binding of the enzyme during immobilization, a reduction in enzyme activity compared to the soluble enzyme and mechanical attrition under conditions of mechanical shear or compressive column pressure.
One of the most widely used commercial resins for the adsorptive immobilization of enzymes possesses a backbone composition of methyl methacrylate cross-linked with trimethylol propane trimethacrylate. Although this resin is capable of sufficient enzyme loadings, it has poor mechanical stability during process applications. For example, the resin easily breaks up under mechanical shear or compressive column pressure, resulting in plugging of the system and reduced expression of catalytic activity.
The object of this invention is the provide new, stable immobilized enzyme preparations which have excellent physical strength and enzyme loading capacity as well as high enzyme activity.